The invention relates to a friction-clutch device equipped with a rotational-drive flywheel.
The object of the invention is, more particularly, in a motor vehicle, to allow automatic stopping and restarting of the internal-combustion engine when the vehicle is at rest for a short periodxe2x80x94vehicle waiting at red lights, for examplexe2x80x94so as to save fuel. Such a clutch device is known because of the document FR-A-2 604 229.
In this document, the clutch device is made up essentially of a conventional friction clutch and of an auxiliary clutch with electromagnetic coupling, arranged between an element integral in rotation with the reaction plate of the friction clutch and an inertial flywheel mounted rotating coaxially with the drive shaft, by means of a ball bearing mounted on an axial spacer interposed between the crankshaft of the engine of the vehicle and the reaction plate.
Referring to FIG. 1 of this document, it is seen that the electric motor driving the inertial flywheel is spaced away radially from the friction clutch, which increases the radial bulk. Moreover, the electromagnetic clutch relies on a plate integral in rotation with the reaction plate while being movable axially with respect to it.
Hence the object of the present invention is to reduce the radial bulk of the clutch device while dispensing with the presence of a plate-type electromagnetic clutch.
According to the invention, a clutch device as indicated above including, on the one hand, a drive flywheel featuring a front extremity for fixing it to a drive shaft, consisting of the output shaft of an internal-combustion engine of a motor vehicle including an engine block, and a rear extremity in the form of a hollow-shaped reaction plate with a central recess delimited externally by a friction face, and, on the other hand, a friction disc comprising at least one friction lining for contact with the friction face of the reaction plate, the said lining being integral with a support coupled to a central hub intended to be integrated in rotation with a driven shaft consisting of the input shaft of a motion gearbox comprising a clutch bell housing at least partly surrounding the reaction plate and [sic] characterised in that the drive flywheel, between its front and rear extremities, carries the rotor of a rotating electric machine comprising a fixed stator coaxial with the rotor, and in that the stator is carried internally by a spacer intended to be integrated with at least one of the engine-block/clutch bell-housing elements.
By virtue of the invention, the radial bulk of the electric-machine/friction-clutch assembly is reduced, since the electric machine is adjacent to the reaction plate and is partly carried by the drive flywheel.
By virtue of the invention, the electric machine is adjacent to the engine block while the reaction plate and the rest of the clutch are accommodated in the usual way within the clutch bell housing. This arrangement makes it possible to modify the engine block and the clutch bell housing of a conventional motor vehicle as little as possible while having a reduced radial bulk due to the fact that the electric machine is offset axially with respect to the friction disc. The rest of the clutch, especially the clutch mechanism, remains unchanged.
The input shaft of the gearbox may be unchanged with respect to that of a conventional vehicle.
In a variant, this shaft may be elongated so as to be centred by means of the crankshaft.
By virtue of the invention, the drive flywheel carries the rotor of an electric machine which makes it possible to dispense with the presence of a plate-type electromagnetic clutch, and the axial bulk is reduced especially because of the absence of a transmission belt.
The electric machine is configured to form a starter for the internal-combustion engine as well as an alternator.
The drive flywheel, called motor flywheel, features very high inertia. The internal-combustion engine, or heat engine, of the vehicle can be cut off at red lights, for example. The flywheel, and thus the heat engine, can easily and rapidly be restarted by the electric machine then playing the role of a starter. It is thus possible to save fuel. Thus the electric machine forms an alternator/starter. It also makes it possible to filter the vibration and to avoid stalling of the heat engine by operating as an electric motor.
For further details on such a machine, refer to the document WO 98/05882.
In one embodiment, the support of the friction lining is coupled elastically to the hub by means of a torsion damper which includes a first guide washer integral with the support and of a second guide washer.
A web linked in rotation, after taking up any play, is interposed between the two guide washers. The second guide washer is installed in the central recess of the reaction plate.
The support may be separate from the first guide washer, being secured to it, for example, by distance rods linking the two guide washers together in such a way that the support is placed next to the first guide washer.
In a variant, the support is in a single piece with the first guide washer.
In one embodiment, the torsion damper penetrates into the central recess of the reaction plate for a reduction in the axial bulk.
In one embodiment, the declutching device of the clutch is of the concentric type in order to reduce the axial bulk between the clutch and the bottom of a bell housing surrounding the friction clutch.
Advantageously, additional bearing means are interposed between the engine flywheel and a carrier piece integral with the spacer fixedly carrying the stator. This results in the possibility of guaranteeing a precise and small gap between the stator and the rotor.
These bearing means may consist of a smooth bearing or of a ball bearing with at least one row of balls. This ball bearing may be instrumented especially in order to measure the speed of rotation of the drive flywheel and thus of the crankshaft.
This carrier piece partly envelops the stator and the rotor and thus advantageously forms a shield avoiding any contamination in the electric machine. This piece is integral, or is affixed integrally onto the spacer.
The drive flywheel may be a single piece with the reaction plate, for reasons of cost.
In a variant, the drive flywheel is in several pieces or parts and, in addition to the reaction plate, includes a tube or a pedestal or a shaft for fixing it onto the drive shaft.
Thus the two pieces of the flywheel may be of two different materials in order to adjust the inertia of the flywheel.
Moreover, it is easily possible to balance the flywheel dynamically, for example by removing material from the outer periphery of the reaction plate.
Furthermore, the dust given off by the friction of at least one of the friction linings which the friction-clutch device includes does not risk contaminating the electric machine since the machine is situated to the front of the reaction plate.
The reaction plate preferably features a skirt at its outer periphery on which is fixed the cover of a friction clutch.
By virtue of this arrangement, no dust coming from the friction linings can soil the electric machine.
This result can also be achieved with the carrier piece when it is adjacent to the reaction plate and partly envelops the rotor and the stator.
This piece constitutes a thermal screen thus sheltering the electric machine.
It will be appreciated that the placing of the second guide washer, in a general way of the friction damper, in the recess of the reaction plate displaces the centre of gravity of the assembly consisting of the electric machine and the friction clutch towards the drive shaft and thus towards the electric machine. By virtue of this arrangement, bearing means can be mounted on the drive flywheel and carry the stator of the machine by way of a carrier piece. Thus, these bearing means will be close to the centre of gravity of the assembly, and thus sheltered. The balancing of the assembly can be carried out easily by adding or removing material to the reaction plate very close to the centre of gravity.
It will be appreciated that the torsion damper may have the configuration desired for damping vibration. It may be thicker and, in addition to the web and the two guide washers, include auxiliary webs in order to increase the angular range of movement between the hub and the friction lining or linings.
The friction clutch may reach high temperatures in service, such that it is appropriate to provide cooling means in order to protect the friction-clutch device as a whole and thus to increase its lifetime.
Advantageously, therefore, the engine flywheel carries means for cooling the electric machine such as fins carried by the reaction plate.
In another embodiment, cooling means are provided in order to cool the stator of the electric machine in order to enhance the lifetime and the performance thereof. It is thus possible to cool the stator directly using piercings formed in it.
Advantageously, the piercings are formed in a single-piece spacer/stator assembly which makes it possible to preserve the mechanical strength of the stator.
Thus, in a variant, the spacer is in a single piece with the stator and the assembly [lacuna] composed of two series of packs of metal plates, one of which forms a spacer.
In a variant, the stator can be cooled by means of external spacer [sic].
Needless to say, these various cooling means can be combined together, for example, a cooling fluid in one embodiment passes through piercings formed in the metal plates of the stator in order to penetrate into a cooling chamber formed in the thickness of the spacer in combination with fins carried by the engine flywheel.
Means for emptying the cooling chamber of the spacer are installed at its low point.
The said emptying means are preferably installed at the lowest point of the said chamber, thus making it possible to empty the complete cooling circuit of the internal-combustion engine of the vehicle.
In one embodiment, the carrier piece of the stator features recesses into which penetrate projections of the engine block in order to reduce the bulk.
The spacer, especially when it consists of two series of packs of metal plates, makes it possible to cool the electric machine by carrying an inlet and outlet duct allowing a flow of air within the electric machine, between the inlet and outlet duct.
One of the ducts may be equipped with an electric-motor/turbine-disc assembly allowing forced air circulation.
The spacer does not need to be centred with respect to the engine block when this spacer is integral with a carrier piece serving to support the abovementioned bearing means. In this case, the clutch bell housing is centred by the spacer, for example, by means of a centring ring passing through the spacer and carried by the engine block.
It will be seen that it is possible to cool the electric machine without impinging on the clutch bell housing or the engine block, especially when the spacer carries an inlet and outlet duct.
The drive flywheel also makes it possible to add material easily and thus to balance the out-of-balance masses of the crankshaft, especially when the heat engine is of three-cylinder type.
The spacer thus makes it possible to perform a large number of supplementary functions. It is also possible to reduce the axial bulk by equipping the friction clutch with a wear-take-up mechanism.